The MAC-TS4 vacuum interrupter tester is the third generation test set which uses our patented technology for determining the condition of vacuum interrupters in the field, shop or laboratory. Utilizing the Penning Discharge Principal, our MAC-TS4 vacuum interrupter test set can easily determine the pressure inside a vacuum interrupter; and, along with wear and number of operations, predict the usable life of the vacuum interrupters used in your circuit breakers and contactors.